There are a number of fact situations where sexual behavior that is not illegal, or is impossible to prosecute, may be unethical.[1] Ethical dilemmas which involve sex can often appear in situations where there is a significant power difference or where there is a pre-existing professional relationship between the participants, when there is an age difference, or where consent is partial or uncertain. Sexual ethics can also include the ethics of procreation.

The terms ethics and morality are often used interchangeably, but sometimes ethics is reserved for interpersonal interactions and morality is used to cover both interpersonal and inherent questions.[2]

However, not all approaches to applied ethics agree that there is an inherent morality:

Moral nihilism is the meta-ethical view that nothing is inherently right or wrong, and that all value judgments are either human constructs, or meaningless.

Moral relativism is the meta-ethical view that moral judgments are subjective. In some cases this is merely descriptive, in other cases this approach is normative - the idea that morality should be judged in the context of each culture's convictions and practices.

Moral universalism is the meta-ethical view that moral judgments are objectively true or false, that everyone should behave according to the same set of normative ethics.

In philosophic terminology, hedonism is the idea that the only intrinsic good is pleasure, making selfish pleasures their primary goal. This may be combined with nihilism in a selfish morality, or with utilitarianism to seek maximization of happiness for everyone. Some religions derive a normative sexual ethics from their texts or teachings, and these range from nihilistic utilitarianism to more complex, fixed systems for determining right and wrong.

Many practical questions arise regarding human sexuality, such as whether sexual norms should be enforced by law, given social approval, or changed. Answers to these questions can be considered on a scale from social liberalism to social conservatism. Considerable controversy continues over which system of ethics or morality best promotes human happiness, and which, if any, is inherently right.

Flirting is an expression of sexuality and a common form of social interaction whereby one person obliquely indicates a romantic and/or sexual interest towards another. However, flirting undertaken for amusement, with no intention of developing any further relationship, poses ethical dilemmas and sometimes faces disapproval from others, either because it can be misinterpreted as more serious, or it may be viewed as "cheating" if the person flirting is already in a romantic relationship with someone else; or if the person to whom flirting is directed is in an exclusive or a serious relationship.

From a human rights and international law perspective, consent is a key issue in sexual ethics. Nevertheless, historically, this has not necessarily been the case. Throughout history, a whole range of consensual sexual acts, such as adultery, fornication, interracial or interfaith sex, 'sodomy' (see sodomy laws) have been prohibited; while at the same time various forced sexual encounters such as rape of a slave, prostitute, war enemy, and most notably of a spouse, were not illegal. The criminalization of marital rape is very recent, having occurred during the past few decades, and the act is still legal in many places in the world. Outside the West, in many countries consent is still not central. For instance, adultery and homosexual acts remain illegal in many countries; and in five countries and in parts of two others homosexual acts carry the death penalty.[3]

Almost all modern systems of ethics insist, as a minimum, that all participants consent to a sexual activity. Sexual ethics (which is reflected in laws) also considers whether a person is capable of giving consent and the sort of acts they can consent to. In western countries, the legal concept of "informed consent" often sets the public standards on this issue. Children, the mentally handicapped, the mentally ill, animals, and people under the influence of drugs like alcohol might be considered in certain situations as lacking an ability to give an informed consent. In the United States, Maouloud Baby v. State of Maryland is a state court case ruling that a person can withdraw sexual consent, and that continuing sexual activity in the absence of consent constitutes rape.

Sexual acts which are illegal, and often considered unethical, because of the absence of consent include rape and molestation. As of 2014, the Model Penal Code: Sexual Assault and Related Offenses, an influential guideline for legislators in the United States published by the American Law Institute was in the process of being rewritten[4] to reflect changing mores in the United States with respect to informed consent.[5] Critics of the proposed changes note that, taken literally, the model law, as written in the 2014 draft, would criminalize attempting to hold a person's hand without prior affirmative consent.[6]

Enthusiastic consent, as expressed in the slogan "Yes means yes," is typically the focus of liberal sexual ethics, rather than marriage.[7][8][9] Under that view passivity, not saying "No," is not consent.[10][6]

Age of consent is also a key issue in sexual ethics. It is a controversial question of whether or not minors should be allowed to have sex for recreation or engage in sexual activities such as sexting. The debate includes whether or not minors can meaningfully consent to have sex with each other, and whether they can meaningfully consent to have sex with adults. In many places in the world people are not legally allowed to have sex until they reach a set age. It is often debated whether or not people under the age of consent are capable of having consensual sexual relationships.

In all cultures, consensual sexual intercourse is acceptable within marriage. In some cultures sexual intercourse outside of marriage is controversial, if not totally unacceptable, or even illegal. In some countries, such as Saudi Arabia, Pakistan,[11] Afghanistan,[12][13] Iran,[13] Kuwait,[14] Maldives,[15] Morocco,[16] Oman,[17] Mauritania,[18] United Arab Emirates,[19][20] Sudan,[21] Yemen,[22] any form of sexual activity outside marriage is illegal.

As the philosopher Michel Foucault has noted, such societies often create spaces or heterotopias outside of themselves where sex outside of marriage can be practised. According to his theory this was the reason for the often unusual sexual ethics displayed by persons living in brothels, asylums, onboard ships, or in prisons. Sexual expression was freed of social controls in such places whereas within society, sexuality has been controlled through the institution of marriage which socially sanctions the sex act. Many different types of marriage exist, but in most cultures that practice marriage, extramarital sex without the approval of the partner is often considered to be unethical. There are a number of complex issues that fall under the category of marriage.

When one member of a marital union has sexual intercourse with another person without the consent of their spouse, it may be considered to be infidelity. In some cultures this act may be considered ethical if the spouse consents, or acceptable as long as the partner is not married, while other cultures might view any sexual intercourse outside of marriage as unethical, with or without consent.

Furthermore, the institution of marriage brings up the issue of premarital sex wherein people who may choose to at some point in their lives marry, engage in sexual activity with partners who they may or may not marry. Various cultures have different attitudes about the ethics of such behavior, some condemning it while others view it to be normal and acceptable.

Premarital sex is sexual activity between two people who are not married to each other. Usually, both parties are unmarried. This might be objected to on religious or moral grounds, while individual views within a given society can vary greatly.[23][24]

In contrast, there are some cultures, groups or individual relationships in which extramarital sex is an accepted norm. In today's western cultures some people practice "polyamory", otherwise known as responsible non-monogamy, or "open marriage". The ethical practice of this necessitates honest dialogue and consent of all those involved.

Most societies disapprove of a person in a position of power to engage in sexual activity with a subordinate. This is often considered unethical simply as a breach of trust. When the person takes advantage of a position of power in the workplace, this may constitute sexual harassment, because subordinates may be unable to give proper consent to a sexual advance because of a fear of repercussions.

Child-parent incest is also seen as an abuse of a position of trust and power, in addition to the inability of a child to give consent. Incest between adults may not involve this lack of consent, and is therefore less clearcut for most observers. Many professional organizations have rules forbidding sexual relations between members and their clients. Examples in many countries include psychiatrists, psychologists, therapists, doctors, and lawyers. In addition, laws exist against this kind of abuse of power by priests, preachers, teachers, religious counselors, and coaches.

Various sexual acts are traded for money or other goods across the world. Ethical positions on sex work may depend on the type of sex act traded and the conditions in which it is traded, there are for example additional ethical concerns over the abrogation of autonomy in the situation of trafficked sex workers.

Sex work has been a particularity divisive issue within feminism. Some feminists may regard sex work as an example of societal oppression of the sex workers by the patriarchy. The ethical argument underlying this position is that despite the apparent consent of the sex worker, the choice to engage in sex work is often not an autonomous choice, because of economic, familial or societal pressures. Sex work may also be seen as an objectification of women. An opposing view held by other feminists such as Wendy McElroy is that sex work is a means of empowering women, the argument here being that in sex work women are able to extract psychological and financial power over men which is a justified correction of the power unbalance inherent in a patriarchal society. Some feminists regard sex work as simply a form of labor which is neither morally good or bad, but subject to the same difficulties of other labor forms.

If sex work is accepted as unethical, there is then dispute over which parties of the contract are responsible for the ethical or legal breech. Traditionally, in many societies, the legal and ethical burden of guilt has been placed largely on the sex worker rather than consumers. In recent decades, in some countries, such as Sweden, Norway and Iceland, the legal burden of prostitution has been moved solely to the consumer.

In ancient Athens, sexual attraction between men was the norm with writers as Plato and Aristophanes writing extensive treatises on the benefits of homosexual love. In the Levant, however, persons who committed homosexual acts were stoned to death at the same period in history that Socrates dallied with young Alcibiades. As presented by Plato in his Symposium, Socrates did not "dally" with young Alcibiades, and instead treated him as his father or brother would when they spent the night sharing a blanket. And in Xenophon's Symposium Socrates strongly speaks against men kissing each other, saying that doing so will make them slavish, i.e., risk something that seems akin to an addiction to homosexual acts.

Most modern secular ethicists since the heyday of Utilitarianism, e.g. T.M. Scanlon and Bernard Williams, have constructed systems of ethics whereby homosexuality is a matter of individual choice and where ethical questions have been answered by an appeal to non-interference in activities involving consenting adults. However, Scanlon's system, notably, goes in a slightly different direction from this, and requires that no person who meets certain criteria could rationally reject a principle that either sanctions or condemns a certain act. Under Scanlon's system it is difficult to see how one would construct a principle condemning homosexuality outright, although certain acts, such as homosexual rape, would still be fairly straightforward cases of unethical behavior.

The human rights of homosexuals are still contested in most parts of the world.

In countries where public health is considered a public concern, there is also the issue of how sex impacts the health of individuals. In such circumstances, where there are health impacts resulting from certain sexual activities, there is the question of whether individuals have an ethical responsibility to the public at large for their behavior. Such concerns might involve the regular periodic testing for sexually transmitted diseases, disclosure of infection with sexually transmitted diseases, responsibility for taking safer sex precautions, ethics of sex without using contraception, leading to an increased level of unplanned pregnancies and unwanted children, and just what amount of personal care an individual needs to take in order to meet his or her requisite contribution to the general health of a nations citizens.